Ah, I just want to add, yes you can track a 
person by their IP, but an IP can also be pirated
or copied.  Which means the person could be 
anyone.  I'm probably not the only anime fan who 
has hacker friends, and anyone could have posted 
that, even me.  I didn't, but why assume it isn't 
someone using the last IP address used to cover 
their tracks?  If I wanted to piss people off and 
say something stupid like that, I wouldn't want 
to be caught.  So, think about motive before you 
accuse.  You know, out right slander in the
US is punishable by jail time.